Vapor pressure measuring apparatus

ABSTRACT

Apparatus measures the vapor pressure of raw crude oil entering a flash tower by measuring operating parameters of the flash tower and its output streams. Flow rates of light component vapor provided by the flash tower and of the flashed crude oil are provided to a vapor pressure sensing network, which also receives signals corresponding to the pressure within the flash tower, to the temperature of the liquid in the flash tower and to the molecular weight and specific gravity of the flashed crude oil. The pressure of the flashed crude oil is then determined utilizing the received signals and equations hereinafter described. The vapor pressure of the flashed crude oil and the vapor pressure of the light component stream, which is substantially constant, is then apportioned according to the relation of the mole flow rates of the light hydrocarbon vapor and the flashed crude oil. The sum of the apportionment is then used to determine the vapor pressure of the raw crude oil.

United States Patent [1 1 laynch et a1.

[ 1 Aug. 26, 1975 VAPOR PRESSURE MEASURING APPARATUS [75] Inventors:Charles R. Lynch, Arthur; Charles W. Harrison, Nederland; Charles L.Kimtantas, Groves; William D. White, Nederland, all of Tex.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: June 28, 1974 [21] Appl. N0.: 484,003

Primary Examiner-Jerry W. Myracle Assistant Examiner.loseph W. RoskosAttorney, Agent, or Firm-T. H. Whaley; C. G. Ries; Ronald G. Gillespie 57 ABSTRACT Apparatus measures the vapor pressure of raw crude oilentering a flash tower by measuring operating parameters of the flashtower and its output streams. Flow rates of light component vaporprovided by the flash tower and of the flashed crude oil are provided toa vapor pressure sensing network, which also receives signalscorresponding to the pressure within the flash tower, to the temperatureof the liquid in the flash tower and to the molecular weight andspecific gravity of the flashed crude oil. The pressure of the flashedcrude oil is then determined utilizing the received signals andequations hereinafter described. The vapor pressure of the flashed crudeoil and the vapor pressure of the light component stream, which issubstantially constant, is then apportioned according to the relation ofthe mole flow rates of the light hydrocarbon vapor and the flashed crudeoil. The sum of the apportionment is then used to determine the vaporpressure of the raw crude oil.

9 Claims, 2 Drawing Figures L|GHT COMPONENTS VAPQR RECORDING MEANS -"'4O[52] US. Cl. 73/64.2

[51] Int. Cl. G0ln 7/16 [58} Field of Search 73/642, 53, 61.3, 36, 73/29[56] References Cited UNITED STATES PATENTS 2,126,052 8/1938 Smith 73/362,949,768 8/1960 Ryant, Jr. et a1, 73/53 3.037.375 6/1962 Jacobs ct a1.74/642 1191,4128 6/1965 Piros 73/53 3,247,708 4/1966 Luthcr 73/533,332,856 7/1967 Hart 73/53 X FLASH VAPOR TOWER PRESSURE L ssnsms RAWCRUDE I6 OIL SIGNAL MEANS SOURCE v4 OF 00 VOLTAGE 6 7 8 FLASHED CRUDEOIL PATENTED AUG26I975 SH ER '& L|GHT COMPONENTS VAPOR SIGNAL MEANSRECORDING MEANS 40 l v VAPOR 2 5| V3 MEANS gQ I30 L V5 v0 E v 22 6 V7 5TV8 VAPOR PRESSURE MEASURING APPARATUS BACKGROUND OF THE INVENTION Fieldof the Invention The apparatus of the present invention relates tomeasuring apparatus in general and, more particularly, to measuringapparatus for refinery units.

SUMMARY OF THE INVENTION Apparatus provides a signal corresponding tothe vapor pressure of a feed hydrocarbon entering a process vessel whichyields a vapor and a processed hydrocarbon liquid. The apparatusincludes a network which samples the processed hydrocarbon liquid andprovides signals corresponding to the molecular weight and the specificgravity of the processed hydrocarbon liquid. Sensors sense the flowrates of the vapor and of the processed hydrocarbon liquid and providecorresponding signals. Other sensors provide signals corresponding tothe sensed pressure of vapor in the vessel and the sensed temperature ofthe hydrocarbon liquid in the vessel. A circuit receiving signals fromthe network and from the sensors provides the feed hydrocarbon vaporpressure signal in accordance with the received signals.

The objects and advantages of the invention will appear more fullyhereinafter from a consideration of the detailed description whichfollows, taken together with the accompanying drawings, wherein oneembodiment of the invention is illustrated by way of example. It is tobe expressly understood, however, that the drawings are for illustrationpurposes only, and are not to be construed as defining the limits of theinvention.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a simplified block diagram ofapparatus, constructed in accordance with the present invention, fordetermining the vapor pressure of crude oil which is being flashed by aflash system also shown in partial schematic form.

FIG. 2 is a block diagram of the vapor pressure sensing means shown inFIG. I.

DESCRIPTION OF THE INVENTION Referring to FIG. 1, a flash tower 1receives raw crude oil through a line 5. The crude oil separates intolight components vapor and into flashed crude oil. The light componentsvapor is removed from flash tower l by way of a line 8 while the flashedcrude oil is removed from flash tower l by way of a line 10. Flow ratesensors 12, 14 provide signals F and F respectively, corresponding tothe flow rates of the light components vapor and the flashed crude oil,respectively, to vapor 7 pressure sensing means 16.

A conventional type pressure transmitter 20 provides a signal Pcorresponding to the sensed pressure in flash tower I to vapor pressuresensing means 16 while a conventional type temperature trnasmitter 22provides a signal T, corresponding to the sensed temperature of theliquid in flash tower l, to vapor pressure sensing means 16.

Signal means 24 samples the flashed crude oil in line and providessignals M and G, corresponding to the average molecular weight and tothe specific gravity,

respectively, of the flashed crude oil. Signal means 24 may be of thesame type shown as signal means 24 in US. Pat. No. 3,733,476. Signals M,G are provided to vapor pressure sensing means 16.

Equations 1 through 5 describe the various relationships that vaporpressure sensing means 16 uses in determining the vapor pressure of theraw crude oil in line MRO MRV where K through K are constants havingvalues of 9.97606, 100, 460, 14.7, 350, 2.6385, 20.0 and 0.46 for aparticular process system; AHVP is an adjusted hydrocarbon vaporpressure in the flash tower corrected to 100F; MRO is a molar rate ofthe flashed crude oil in units of lb. moles of liquid per hour; MRV isthe molar rate of the vapor in units of lb. moles of gas per hour andRVP is the Reid Vapor Pressure of the raw crude oil.

Vapor pressure sensing means 16 receives direct current voltages V to Vfrom a source 30 of direct current voltages and provides a signal Ecorresponding to the vapor pressure of a petroleum fraction to recordingmeans 40. Voltages V to V correspond to the constants K, through Kdescribed in Equations 1 through 5, above. Recording means 40 recordssignal E, from vapor pressure sensing means 16.

Referring now to FIG. 2 vapor pressure sensing means 16 includes summingmeans 50 which sums pressure signal P with voltage V, to provide asignal corresponding to the term P+K to a natural log function generator53. Generator 53 provides a signal corresponding to the term ln(P+K tosumming means Summing means 60 and subtracting means 63 sums signal Twith voltage V;, and subtracts signal T from voltage V respectively.Summing means 60 provides a signal, corresponding to the term (T-l-K toa divider 68 while subtracting means 63 provides a signal, correspondingto the term (K -T), to a multiplier 70. Multiplier 70 multiplies voltageV with the signal from subtracting means 63 to provide a signal todivider 68. Divider 68 divides the signal from multiplier 70 with thesignal from summing means 60 to provide a signal to summing means 54.

Summing means 54 sums the received signals to provide a signal,corresponding to the term A, to a convention type exponential functiongenerator which in turn provides a signal corresponding to the term AHVPin equation 1.

A multiplier multiplies flow rate signal F with specific gravity signalG to provide a signal to a multiplier 81. Multiplier 81 multiplies thesignal from multiplier 80 with voltage V; to provide a signal to divider82. Divider 82 divides the signal from multiplier 81 with signal M toprovide a signal corresponding to the molar rate MRO of the flash crudeoil. A multiplier 84 multiplies the signal from divider 82 with thesignal from generator 75 to provide a signal corresponding to the term(AHVP)(MRO) in equation 5.

A multiplier 87 multiplies flow rate signal F with voltage V to providea signal corresponding to the molar rate MRV for the vapor in line 8.Summing means 90 sums the signal from divider 82 with the sig nal frommultiplier 87 to provide a signal corresponding to the term (MRO+MRV). Adivider 93 divides the signal provided by multiplier 84 with the signalfrom summing means 90 to provide a signal corresponding to the term(AHVP) (MRO) (MRO) (MRV) A multiplier 95 multiplies the signal frommultiplier 87 with voltage V to provide a signal corresponding to theterm (K )MRV in equation 5. A divider 98 divides the signal provided bymultiplier 95 with the signal provided by summing means 90 to provide asignal corresponding to the term (MRO MRV) Summing means 100 sums thesignals from dividers 93, 98 to provide a signal to subtracting means103. Subtracting means 103 subtracts voltage V from the signal providedby summing means 100 to provide signal E corresponding to the Reid VaporPressure RVP of the raw crude oil.

The apparatus of the present invention as hereinbefore describedprovides an output corresponding to the Reid Vapor Pressure of raw crudeoil entering a flash tower while monitoring the operation of the flashtower so as to provide an on-line determination of the Reid VaporPressure. The apparatus of the present invention as heretofore describedis not restricted to the determination of the Reid Vapor Pressure of rawcrude oil but is also applicable to the vapor pressure of anyhydrocarbon liquid entering a process vessel which provides a vapor anda processed hydrocarbon liquid as well as other chemical processes.

It would be obvious to one skilled in the art that a general purposedigital computer could be utilized to determine the Reid Vapor Pressureof the raw crude oil. Signals F F T, G, M and P would be converted todigital signals using conventional type analog-todigital converters. Thedigital computer may provide its own record or output digital signals.The output digital signals would then be converted to signal E by adigital-to-analog converter.

What is claimed is:

1. Apparatus for providing an output signal corresponding to the vaporpressure of a feed fluid entering a process vessel which yields a vaporand a processed liquid, comprising means for sampling the processedliquid and providing signals corresponding to the molecular weight M andthe specific gravity G of the processed liquid, means for sensing theflow rates F and F of the vapor and the processed liquid and providingsignals corresponding thereto, means for sensing the pressure P of vaporin the vessel and providing a corresponding signal, means for sensingthe temperature T of liquid in the vessel, and means connected tosampling means and to all the sensing means for providing the outputsignal corresponding to the vapor pressure of the feed fluid inaccordance with the F F P, T, M and G signals from the sampling meansand the sensing means.

2. Apparatus as defined in claim 1 in which the feed fluid is ahydrocarbon liquid, and the processed liquid is a processed hydrocarbonliquid.

3. Apparatus as defined in claim 2, in which the output signal meansincludes means connected to the pressure and temperature sensing meansfor providing a signal corresponding to a term A in accordance with theP and T signals from the pressure and temperature sensing means and thefollowing equation:

where K through K are constants, and network means connected to the Asignal means for providing the AHVP signal in accordance with the Asignal and the following equation:

4. Apparatus as defined in claim 3 in which the output signal meansincludes means connected to the sampling means and to the flow ratesensing means for providing a signal corresponding to the molar rate MROof the processed hydrocarbon liquid in accordance with M and G signalsfrom sampling means and the F signal from the flow rate sensing means,and means connected to the flow rate sensing means for providing asignal corresponding to the molar rate MRV of the vapor in accordancewith the F signal from the flow rate sensing means.

5. Apparatus as defined in claim 4 in which the MRO signal meansprovides the MRO signal in accordance with the F M and G signals and thefollowing equation:

(m (K5) MRO M where K is a constant, and the MRV signal means providesthe MRV signal in accordance with the F signal and the followingequation:

where K is a constant.

6. Apparatus as defined in claim 5 in which the out put signal meansincludes summing means connected to the MR0 and the MRV signal means forproviding the output signal in accordance with the sum of the MRV andMR0 signals.

7. Apparatus as defined in claim 6 further comprising means connected tothe summing means for recording the output signal.

8. Apparatus as defined in claim 6 in which the process vessel is aflash tower, the feed hydrocarbon is raw crude oil, the processedhydrocarbon is flashed crude oil, and the vapor is light components gas.

9. Apparatus as defined in claim 5 in which the constants K through Khave values of 9.97606, 100, 460, 350 and 2.6385, respectively.

UNITED STATES PATENT AND TRADEMARK OFFICE QEIFICAT 9F CGRRECTIQN PATENTNO. 3901062 DATED AUGUST 26, 1975 INVENTOR(S) 2 CHARLES R. LYNCH;CHARLES W HARRISONgCHARLES L KIMTANTAS; WILLIAM D. WHITE It Is certrfredthat error appears m the above-ldentrfred patent and that sad LettersPatent are hereby corrected as shown below:

Claim 3, line 25 "AHVP=e should read --AHVP=e Signed and Scaled thisfinest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner 0] Patent:and Trademarks

1. Apparatus for providing an output signal corresponding to the vaporpressure of a feed fluid entering a process vessel which yields a vaporand a processed liquid, comprising means for sampling the processedliquid and providing signals corresponding to the molecular weight M andthe specific gravity G of the processed liquid, means for sensing theflow rates F1 and F2 of the vapor and the processed liquid and providingsignals corresponding thereto, means for sensing the pressure P of vaporin the vessel and providing a corresponding signal, means for sensingthe temperature T of liquid in the vessel, and means connected tosampling means and to all the sensing means for providing the outputsignal corresponding to the vapor pressure of the feed fluid inaccordance with the F1, F2, P, T, M and G signals from the samplingmeans and the sensing means.
 2. Apparatus as defined in claim 1 in whichthe feed fluid is a hydrocarbon liquid, and the processed liquid is aprocessed hydrocarbon liquid.
 3. Apparatus as defined in claim 2, inwhich the output signal means includes means connected to the pressureand temperature sensing means for proViding a signal corresponding to aterm A in accordance with the P and T signals from the pressure andtemperature sensing means and the following equation:
 4. Apparatus asdefined in claim 3 in which the output signal means includes meansconnected to the sampling means and to the flow rate sensing means forproviding a signal corresponding to the molar rate MRO of the processedhydrocarbon liquid in accordance with M and G signals from samplingmeans and the F2 signal from the flow rate sensing means, and meansconnected to the flow rate sensing means for providing a signalcorresponding to the molar rate MRV of the vapor in accordance with theF1 signal from the flow rate sensing means.
 5. Apparatus as defined inclaim 4 in which the MRO signal means provides the MRO signal inaccordance with the F2, M and G signals and the following equation: 6.Apparatus as defined in claim 5 in which the output signal meansincludes summing means connected to the MRO and the MRV signal means forproviding the output signal in accordance with the sum of the MRV andMRO signals.
 7. Apparatus as defined in claim 6 further comprising meansconnected to the summing means for recording the output signal. 8.Apparatus as defined in claim 6 in which the process vessel is a flashtower, the feed hydrocarbon is raw crude oil, the processed hydrocarbonis flashed crude oil, and the vapor is light components gas. 9.Apparatus as defined in claim 5 in which the constants K1 through K6have values of 9.97606, 100, 460, 350 and 2.6385, respectively.